Device and process for converting hydrocarbons



June 23, 1953 R. A. FINDLAY DEVICE AND PROCESS FOR CONVERTING HYDROCARBONS Filed Aug. l0, 1950 4 m .l M u 7 m TIN 8 9 n .sa 2 w 3 2 five m n um/ 3 n L m 3 e QA ln 9 1 -7 L l .l Il n 3 Il l u C u 4 1|||1 .|6 l W n u 5 C n .||n UO w 1K5# 4 mc u n u n u n u 3 L T ||:2 @C n W 1 P D M m u u u u P n n n .-IILF i-:l---|||l|||-|||Ll|1mlwn1mll m d l- 1 I o A l l n l I l l n l l l l u r l l I l l l l l l l l .IL w r 4 l l n n I I l n l l l l n l l l :IL

ATTORNEYS Patented June 23, 1953 DEVICE AND PROCESS FOR CONVERTING HYDROCARBONS Robert A. Findlay, Bartlesville, Okla., assigner to Phillips Petroleum Company, a corporation of Delaware Application August 10, 1950, Serial No. 178,737

8 Claims.

This invention relates to the conversion of hydrocarbons. In one of its more speciiic aspects, it relates to a process for cracking hydrocarbon oils at high temperatures. In another of its more specic aspects, it relates to a semicontinuous process for converting hydrocarbon oils to lower boiling products. In another of its more specic aspects, it relates to an improved system for converting heavy residual oils to lower boiling products in a semi-continuous manner.

I-Ieavy residual oils have long posed a considerable problem in the petroleum industry. Although the refining technique of the petroleum industry has improved greatly during the past several years, heavy residual oils have been of little or no value because of the great tendency of such materials to form and deposit coke, tar, and other carbonaceous materials in rening equipment. As the demand for petroleum products has has increased, that demand has placed a greater burden upon the available natural resources of the world and has focused attention more directly upon what heretofore had been deemed waste material. Heavy residual oils are very closely akin to waste materials and it is believed therefore that any process which aids in the utilization of such materials is of very great importance.

Many processes have been set forth in the petroleum art by which it has been proposed to convert heavy residual oils to provide normally lighter materials such as hydrogen, gasoline stocks, and other hydrocarbon products. As pointed out above, however, the tendency for such materials to form carbonaceous deposits has made such processes relatively uneconomical. Recent developments in petroleum conversion techniques have utilized pebble heater apparatus for converting heavy residual oils to lower boiling materials. Such improved techniques still, however, have inherent disadvantages. One of the main disadvantages of using pebble heater apparatus in the conversion of heavy residual oils as in the conversion of other hydrocarbon oils and lighter hydrocarbons is that during the conversion, a portion of the reaction products comes in contact with the reaction chamber or gaseous eiuent outlet for a period of time sufiicient to allow those materials to be converted to coke thereon. The coke lay-down develops to such an extent that pressure drop through the chamber becomes excessive. I have devised a process and a system whereby the disadvantages resulting from the tendency for products oi such hydrocarbons to develop coke deposits about the product outlet conduit in the reaction chamber are overcome by reason of the fact that I utilize an alternating semi-continuous process for the conversion of such materials. In this process the coke is burned from one chamber while heating particulate solid heat exchange material therein.

Broadly speaking, this invention comprises heating a bed of particulate solid heat exchange material Within a first heat exchange chamber, passing that heated solid heat exchange material into a second heat exchange chamber in which it is caused to contact heavy residual oil or other hydrocarbon oil or hydrocarbons supplied thereto as a reactant material, raising the reactant material to reaction temperature by the direct heat exchange between the reactant material and the hot solid heat exchange material, and removing reaction products from the second heat exchange chamber. As the reaction proceeds within the second heat exchange chamber, tar vapors and hydrocarbon products contact the reaction chamber or product outlet until a portion thereof is converted to coke thereon. As coke builds up in that chamber so as to unduly increase the pressure drop therethrough, reactant materials are diverted from the second chamber, heating material is diverted from the first chamber, the rst and second heat exchange chambers are purged with a purging gas, such as steam, and the second heat exchange chamber is converted to a heating chamber for heating the solid heat exchange material and the first heat exchange chamber is converted to a reaction chamber.

An object of this invention is to provide an improved method for converting hydrocarbons. Another object of Vthe invention is to provide an improved system for converting hydrocarbons. Another object of the invention is to provide an alternating semi-continuous method for converting hydrocarbon oils in pebble heater apparatus. Another object of the invention is to provide a method for converting hydrocarbon oils at an increased rate. Another object of the invention is to overcome the problem of coke accumulation in pebble heater apparatus during conversion of hydrocarbon oils to normally lower boiling materials, such as hydrogen, aromatic distillates, and normally gaseous materials, such as ethylene, propylene, acetylene, and the like. Other and further ,objects and advantages will be apparent to those skilled in the art upon study of the accompanying disclosure and the drawing.

Solid heat exchange material which may be utilized in the pebble heater system of this invention is generally termed pebbles The term pebbles as used herein denotes any substantially solid material of flowable size and form which has sufficient strength to withstand mechanical pressures and the temperatures encountered within the pebble heater system. These pebbles must be of such structure that they can carry large amounts of heat from one chamber to another without rapid deterioration or substantial breakage. Pebbles which may be satisfactorily used in this hydrocarbon conversion system may be substantially spherical in shape and range from about one-eighth inch to about one inch in diameter. The pebbles are preferably of a size within the range of from one-eighth inch to ve-eighths inch in diameter. Materials which may be used singly or in combination in the formation of such pebbles include among others alumina, silicon carbide, periclase, beryllia, mullite, nickel, cobalt, copper, iron, magnesia, and silica.

More complete understanding of the invention will be obtained upon reference to the schematic drawing which is a diagrammatic elevation of apebble heater apparatus, together with a flow plan utilized in the automatic operation of this system.

Referring particularly to the device shown in the drawing, heat exchange chamber II is provided With a hydrocarbon feed inlet conduit I2 in its upper end portion having flow control valve I3 provided therein. Gaseous eiiiuent outlet conduit I4, having flow control valve I5 provided therein, is also provided in the upper end porf tion of heat exchange chamber Il. Product co1- lector system I6 is provided intermediate the ends of heat exchange chamber Il and may be any conventional type of gaseous material collector system utilized in pebble heater apparatus and the like. Product outlet conduit I1, having flowV control valve I8 provided therein, extends between product collector system I6 and a product disposal point, not shown. Inlet conduit I9 is connected t'o the lower portion of heat exchange chamber II and, preferably as header member 20, extends at least a portion of the way around the lower part of that chamber communicating with the interior of the chamber through the wall thereof. steam inlet conduit 2I having flow control valve 22 provided therein. Fuel inlet conduit 23, having now control valve 24 provided therein is also connected to inlet conduit i9. Air inlet conduit 25, having flow control valve 28 provided therein, is also attached to inlet conduit I9. It should be obvious to those skilled in the art that considerable modification of this combination of inlets can be made without departing from the spirit or the scope of this disclosure. The combination of gaseous material inlets to form a single gaseous material inlet is, however, believed to be the most feasible method of operation of this chamber.' Igniter means 21, which may be any conventional means for igniting a gaseous fuel material, such as a spark plug or the like, is provided so as to communicate with the interior of the lower portion of heat exchange chamber II, preferably at a point adjacent gaseous material inlet header 20.

Heat exchange chamber 29 is provided in its upper end portion with a reactant material inlet conduit 3| having flow control valve 32 provided therein. Reactant material inlet conduit I2 and conduit 3l may be connected together as shown Connected to inlet conduit I9 is in the drawing or may extend separately from a reactant material supply source, not shown. Solid heat exchange material conduit 33 extends between the lower portion of heat exchange chamber II and the upper end portion of heat exchange chamber 29. Gaseous material inlet conduit 34 is provided-for the introduction of an inert gas, such as steam, or some other hot gaseous material which is inert to the reaction, into solid heat exchange material conduit 33. Gaseous etliuent outlet conduit 35 having flow control valve 36 provided therein, extends from the upper end portion of heat exchange chamber 29. Product collector 31, which is similar to collectorv system I6, is provided intermediate the ends of heat exchange chamber 29. Product outlet conduit 3,8, having ilow control valve 39 provided-therein, extends between product collector system 31 and a product disposal point, not shown. Product outlet conduits I1 and 38 are preferably connected, as shown in the drawing, but these conduits may in one modification of the invention extend as separate conduits to a product disposal, point. Inlet conduit 4I is connected to the lower end portion of heat exchange chamber 2'9 and extends preferably as header member 42 around at least a part of the lower portion of chamber 29 and communicates with the interior thereof through its lower wall portion. Steam inlet conduit 43, having flow control valve 44 provided therein, fuel inlet conduit 45, having flow control valve 46 provided therein, and air inlet conduit 41, having now control valve 48 provided therein, are connected to inlet conduit 4| in the `same manner as are conduits 2l, 23, and 25 connected to conduit I9. Igniter means 49, which is similar to igniter means 21, is provided in the lower portion of heat exchange chamber 29 for igniting a gaseous fuel material therein. Solid material outlet conduit 5I extends Afrom the lower portion of heat exchange chamber 29 to the lower portion of elevator 52. lElevator 52 is connected at its upper end portion'to solid material inlet conduit 53 which extends in to the upper end portion of heat exchange chamber I I. In the specific showing of the drawing, elevator 52 is a gas lift-type elevator, entraining gas being introduced thereinto through inlet conduit 54. Separator 55 is provided at the upper end portion of elevator 52 and is provided with gaseous material outlet conduit 56 therein.

In the operation of this invention pebbles are introduced into the upper portion of heat exchange chamber II through inlet conduit 53 and form a flowing contiguous pebble mass therein. A gaseous fuel and air are introduced into the lower portion of heat exchange chamber I I and burned in the lower portion of that chamber in contact with the pebbles gravitating through that chamber. The system may be modif-led by introducing a hot combustion gas directly in contact with the gravitating pebbles within chamb er VII. The hot combustion gases introduced directly into chamber II are formed by burning fuel on the surface vof the pebbles 'and pass upwardly through Ithe gravlntatinfr mass of pebbles, heating those pebbles vto a high temperature, the specific temperatu're'depending upon the desired reaction products from the system. When hydrocarbon oils are converted to normally gaseous materials or high aromatic gasoline constituents, reaction temperatures between 1000 F. and 2500" F. are ordinarily utilized', preferably 1100.o F. 'to 1600" F. Forproduction of materials,

such as acetylene, higher temperatures in the range of between 1800 F. and 2500" F. are required. The temperature of the pebbles within the heating chamber is preferably about 200 F. above the highest desired reaction temperature within the reaction chamber. The combustion gases are removed from chamber I I through gaseous efliuent outlet conduit I4.

Pebbles which have been heated to reaction temperature in heat exchange chamber II are gravitated through solid material conduit 33 into the upper portion of heat exchange chamber 29 and form a flowing contiguous pebble mass therein. Hydrocarbon oil is introduced through conduit di into the upper portion of chamber and is distributed over the surface of the hot pebbles within that chamber. The hydrocarbon oil can be introduced over the surface of the pebbles at a point within solid material conduit 355. The hydrocarbon oil is raised to reaction temperature in its direct heat exchange with the hot pebbles and the reaction products are caused to flow concurrently with the pebbles in chamber downwardly to a point intermediate the ends of that chamber where they are collected by product collector system 37 and are removed from chamber 2Q by means of product outlet conduit 33. The product materials contact the product outlets for a sufcient period of time that a portion thereof is converted to coke on the outlet conduit. Pebbles which are cooled in the reaction cf the hydrocarbon oil are gravitated from heat exchange chamber 29 through conduit lll and are entrained by introduction of a gas introduced through conduit 54 into ele vator rlhe pebbles are elevated through elevator to separator 55 in which the pebbles and the entraining gas are separated, the en training gas being removed therefrom through conduit The pebbles are gravitated through conduit into the upper portion of heat exchange chamber II.

As the colte deposits Within heat exchange chamber 29 begin to cause excessive pressure drop therein, valves 32 and 39 are closed as are valves iid and 26. Valves 22, 36, and 114 are opened and heat exchange chambers II and 29 are purged with steam for a very few minutes. Generally one to two minutes are suiiicient to purge the chambers. Valves I 5, 22, and e4 are ien closed and valves i3, lil, 45, and 138 are opened. igniter means 159 ignites fuel which is ed into the lower portion of chamber 2S f pebr s within chamber 29 are heated in a ,incr similar to that described in connection Sth the heating of pebbles within chamber II. hi i has been deposited upon the surface bles within, the reaction chamber may, with other coke formation in chamber be utilized as a portion of the heating ma- .1 in that chamber by controlling the intro= duction of an amount of air thereinto in excess of that required to support the fuel introduced into chamber 2e. Hydrocarbon oil is introduced into the upper portion of heat exchange chamber ii in the same manner as described above in connection with the operation of chamber 2t. rSfhe system is operated in this manner until coke deposits within chamber I I begin to cause excessive pressure drop therein, at which time approvalves are closed and other appropriate valves are opened so as to purge each of the chambers with steam. Chamber II is then placed onstream as the pebble heating chamber, and chamber 2S is once again placed onstream-as .a er

6 the reaction chamber. Products removed from chambers II and 253 are quenched in a conventional manner, not shown, at a point downstream of valves lil and 39.

The operation of this system is conveniently adapted to automatic operation by utilizing a time cycle controller such as an impulse-sequence time-cycle controller, which may be purchased on the open market, to periodically7 control the appropriate valves and automatically change the opera-tion of the individual chambers at given time intervals. The impulsa-sequence time-cycle controller described in lThe Bristol Company bulletin C305, August i948, is advantageously used in this invention. Impulse-sequence cycle controller El is adapted so that control I actuates valves Siiand Saso as to shut oif the flow of material through conduits 3| and 3E at a predetermined time. Control 3 opens valve 36 and oontrol ii closes valves 2li and 2E. Control l opens valve 22 to allow steam to flow upwardly through chamber i l so as to purge combustion gas therefrom. The steam and combustion gas are removed through conduit Ill. Control li opens valve so as to allow steam to flow upwardly through and purge chamber 29 and the steam and purged materials are removed through outlet conduit 35. At the end of a given period of time, ordinarily one to ten minutes being sufcient, preferably l to 2 minutes, control t closes valve et, control 2 opens valves ifi and i3 and actuates igniter de to ignite the fuel introduced into the lower portion of chamber 29 through header member Control l closes valve 22. Control t closes valve le and control 8 opens valves I3 and itl. Pebbles are thus heated within chamber and are elevated to the upper portion of chamber i l in which the hydrocarbon reactant materials are distributed over the surface thereof. The reaction of the hydrocarbon oil is carried on within chamber I I as described above in connection with the operation of chamber 29. The resulting products are removed from that chamber through product collector system I6 and product outlet conduit il. Coke deposits are desirably removed at the end of a predetermined period, preferably within the range of 3 to 8 hours. The amount of coke which is deposited in such a manner as to undesirably increase pressure drop through the system will depend upon the particular reactant material and the reaction conditions within the chamber.

Control 6 opens valve l5, control l opens valve 22, control il closes valves I3 and I8, control 2 closes vvalves l5 and 4S, and control 4 opens valve Lift. Each of the heat exchange chambers is purged with steam in this manner for a purging period, preferably of about one to 2 minutes. Impulse-sequence cycle controller 57 once again operates, causing control 'I to close valve 22, control i to open valves 2d and 26, and to actuate igniter means El' to ignite the fuel introduced into heat exchange chamber I I through header member 25%. Control@ closes valve at, control 3 closes valve ihand control i opens valves 32 and 39. The heating of pebbles within chamber I I and reaction of reactant materials within chamber 2t, and removal of resulting reaction products from chamber is through product outlet conduit is similar to that described above. Operation of each cycle of this system is preferably within the range of from 3 to 8 hours depending upon the type of oil being converted. Longer periods of operation may be obtained by slight modifica- 7 tion of the impulse-sequence time-cycle controller, however.

This system may be modied so as to operate in response to a pressure differential within the reaction chamber by adapting differential pressure controllers to actuate impulse-sequence time-cycle controller l. The impulse-sequence time-cycle controller can be set so as to operate up to the final minute of its cycle, at which time it will be cut out automatically according to adjustment. As the pressure differential within the reaction chamber rises to an undesirable limit, such as for example 5 p. s. i. g., the appropriate pressure differential controller will actuate impulse-sequence time-cycle controller 51 to cause that controller to once again go into operation causing appropriate valves to be closed and opened so as to purge veach of the chambers with steam, and appropriate valves to then be opened and closed so as to alternate the heat exchange chambers as heating and reaction chambers. The impulse sequence time cycle controller1 then operates up to the last minute of its set cycle, at which time it once again is automatically cut on of operation until it is again set in operation by the operation of the appropriate differential pressure controller operating with the chamber currently being utilized as a reaction chamber.

Although this invention has been particularly described in connection with the conversion of hydrocarbon oils, particularly heavy residuum oil, this invention is also advantageously utilized in the conversion of gaseoushydi'ocarbons.

Many modifications of this invention will be apparent to those skilled in the art upon study of the accompanying disclosure and the drawing. It is believed that such modications are clearly within the spirit and the scope of this disclosure.

I claim:

1. A semi-continuous process for converting hydrocarbons to lower boiling products which comprises heating pebbles Ato a temperature o at least 1200 F. in a first chamber of a pebble heater system by direct heat exchange with a hot heating gas; passing said hot pebbles through a second chamber of said Ypebble heater system; heating hydrocarbons to Vreaction temperature by direct contact with said hot pebbles in said second chamber.; removing reaction products from said second chamber; returning pebbles from said second to .said first chamber; `purging said -first andsecond chambers of hot heating gas, hydrocarbons land reaction products upon excessive increase Yof pressure drop through said second chamber; reversing operation of said pebble heater system by heating said pebbles to a temperature of at least 1200o F. by direct heat exchange with a hot heating gas in said second chamber; passing said hot pebbles through said rst chamber; introducing hydrocarbons into direct heat exchange with said hot pebbles in said first chamber; heating said hydrocarbons to re action temperature by said direct contact with said hot pebbles in said nrst chamber; removing resulting reaction products from said rst chamber; returning pebbles from said iirst to said second chamber; purging said second and first chambers of hot heating gas, hydrocarbons and reaction products upon excessive increase of pressure drop through said rst chamber; and similarly reversing operation of said pebble heater system Aas pressure drop through the chamber containing fthe hydrocarbon reaction becomes excessive.

2. A semi-continuous process for converting hydrocarbon oils to lower boiling products which comprises continuously and serially gravitating solid heat exchange material through a first heat exchange chamber and a second heat exchange chamber and recycling said solid heat exchange material to said rst heat exchange chamber; heating said solid heat exchange material to a temperature in the range of between 1200 F. and 2700 F. in said rst heat exchange chamber by direct heat exchange with hot gaseous heat exchange material; introducing hydrocarbon oil into the upper portion of said second heat exchange chamber in direct heat exchange with said hot solid heat exchange material therein, whereby said hydrocarbon oil is raised to reaction temperature; removing resulting reaction products from a point intermediate the ends of said second heat exchange chamber; discontinuing the flow of hot gaseous heat exchange material and hydrocarbon oil to said rst and second chambers prior to the development of excessive pressure drop through said second chamber; purging said first and second chambers with a purge gas for a short period of time; heating said solid heat exchange material to a temperature within the range of between i200o F. and 2700 F. and oxidizing any coke said second heat exchange chamber by passing a hot gaseous heat exchange material together with an excess of oxygen therethrough; introducing hydr car bon oil into the upper portion of said nrst heat exchange chamber; raising said hydrocarbon oil to reaction temperature by direct heat exchange between said oil and said hot solid heat exchange material from said second chamber; removing resulting reaction products from a point intermediate the ends of said iirst heat exchange chamber; discontinuing the flow of hot g seous heat exchange material and hydrocarbon oil to said first and second chambers prior to the development of excessive pressure drop through said irst chamber; purging said first and second heat exchange chambers with a purge gas for a short period of time; and similarly periodically reversing operating of said heat exchange chami bers as heating and reaction chambers in said process as pressure drop through the chamber containing the hydrocarbon reaction becomes ex cessive.

3. A process of claim 2 wherein said solid heat exchange material is heated in each heat ex change chamber during its operation as a heating chamber to a temperature within the range oi between 1300 F. and 1800 F.

4. A process of claim 2 wherein said solid heat exchange material is heated in each heat exchange chamber during its operation as a heating chamber to a temperature within the range of between 2000" F. and 2700 F.

5. A semi-continuous process for converting hydrocarbon oil to lower boiling products which coniprises gravitatingparticulate solid heat exchange material through a first heat exchange zone in direct heat exchange with hot gaseous heat exchange material, whereby said solid material is heated to a temperature within the range oi` between 1200D F. and 2700o F.; gravitating said hot solid heat exchange material into the upper portion of a second heat exchange zone and downwaidly therethrough; introducing hydrocarbon oil into the upper portion of said second heat exchange zone in direct heat exchange with said hot solid vheat exchange material; converting at least a portion of said hydrocarbon oil to lower boiling materials in said second heat exchange zone; withdrawing resulting reaction products from a point intermediate the ends of said second heat exchange zone; passing solid heat exchange material from the lower portion of said second heat exchange sono into the upper portion of said first heat exchangefzone; stopping flow of said hot gaseous heat exchange material and hydrocarbon oil through said first and second heat exchange zones at the end of a period with in the range of between 3 and 8 hours; passing steam upwardly through said first and second heat exchange zones for a period of between 1 and l minutes, whereby said first and second heat exchange zones are purged of said hot gaseous exchange material, said hydrocarbon oil and reaction products; stopping the flow of steam through said first and second heat ex-1 change zones; passing hot gaseous heat exchange material and an -excess of oxygen through said second heat exchange zone in direct heat ex change with said solid heat exchange material and removing any colte deposited in that chamber by oxidation thereof with said excess Aof oxygen, whereby said solid heat exchange material is raised to a temperature within the range of between 1206" F. and 2700 F.; introducing hydrocarbon oil into the upper portion of said first heat exchange zone in direct heat exchange with said hot solid heat exchange material therein, whereby said hydrocarbon oil is raised to reaction temperature; removing resulting reaction products from a point intermediate the ends of said first heat exchange zone; stopping the flow of hot gaseous heat exchange material and air and hydrocarbon oil to said second heat exchange zone and said first heat exchange zone at the end of a period within the range of 3 to 8 hours; passing steam upwardly through said irst and second heat exchange zones so as to purge those Zones of other gaseous materials; and similarly reversing operation of said heat exchange zones to alternate them as heating and reaction zones in said process.

6. The process of claim 5, wherein said hot gaseous heat exchange material is combustion gas formed by burning a fuel on the surface of said solid heat exchange material; and said fuel is automatically ignited upon its introduction into the heat exchange Zone utilized for heating said solid heat exchange material.

7. An improved pebble heater system which coniprises in combination a first closed upright elongated chamber; a pebble inlet conduit in the upper end of said first chamber; a first gaseous efuent conduit in the upper end portion of said iirst chamber; a iirst valve in said first gaseous effluent oonduit; a first reactant material inlet conduit in the upper end portion of said rst chamber; a second valve in said first reactant material inlet conduit; a first product collector intermediate the ends of said first chamber; a first product outlet connected to said first product collector means and extending from said rst chamber; a third valve in said first product outlet conduit; a first fuel inlet conduit connected to the lower portion of said first chamber; a fourth valve in said rst fuel inlet conduit; a first steam inlet conduit connected to the lower portion of said iirst chamber; a fifth valve in said rst steam inlet conduit; a first air inlet conduit connected to the lower portion of said rst chamber; a sixth valve in said nrst air inlet conduit; an igniter in the lower portion of said first chamber; a second closed upright elongated chamber below said first chamber; a

pebble conduit extending between the lower porn tion of said first chamber and the upper end portion of said second chamber; a second gaseous effluent conduit in the upper end portion of said second chamber; a seventh valve in said second effluent conduit; a second reactant material inlet conduit in the upper end portion of said second chamber; an eighth valve in said second reactant material conduit; a second product collector intermediate the ends of said second chamber; a second product outlet conduit connected to said second product collector and extending from said second chamber; a ninth valve in said second product conduit; a second fuel conduit connected to the lower portion of said second chamber; a tenth valve in said second fuel conduit; a second steam conduit connected to the llower portion of said second-chamber; an eleventh valve in said second steam conduit; a second air inlet conduit connected to the lower portion of said second chamber; a twelfth valve in said second air inlet conduit; av second' igniter in the lower portion of said second chamber; a pebble outlet conduit in the lower end of said second chamber; an elevator connecting saidpebble outlet conduit from said second chamber and said pebble inlet conduit in said first chamber; and an impulsesequence cycle controller having a plurality of controls therein, a rst control thereof operatively connected to said eighth and ninth valves, a second control thereof operatively connected to said tenth and twelfth valves and said second igniter, a third control thereof operatively connected to said seventh valve, a fourth control thereof operatively connected to said eleventh valve, a nfth control thereof operatively connected to said fourth and sixth valves and said first igniter, a seventh control thereof operatively connected to said fifth valve, and an eighth control operatively connected to said second and third valves.

8. An improved pebble heater system which comprises in combination a rst closed upright elongated chamber; a pebble inlet conduit in the upper end of said first chamber; a rst gaseous eiiluent conduit in the upper end portion of said first chamber; a first valve in said first gaseous efluent conduit; a rst reactant material inlet conduit in the upper end portion of said rst chamber; a second valve in said first reactant material inlet conduit; a first product collector intermediate the ends of said first chamber; a first product outlet conduit connected to said first product collector means and extending from said first chamber; a third valve in said rst product outlet conduit; a first fuel inlet conduit connected to the lower portion of said first chamber; a fourth valve in said first fuel inlet conduit; a first steam inlet conduit connected to the lower portion of said first chamber; a fifth valve in said first steam inlet conduit; a first air inlet conduit connected to the lower portion of said first chamber; a sixth valve in said first air inlet conduit; an igniter in the lower portion of said nrst chamber; a second closed upright elongated chamber below said first chamber; a pebble conduit extending between the lower portion of said first chamber and the upper end portion of said second chamber; a second gaseous effluent conduit in the upper end portion of said second chamber; a seventh valve in said second eluent conduit; a second reactant material inlet conduit in the upper end portion of said second chamber; an eighth valve in said second reactant material conduit; a second product collector intermediate the ends of said second chamber; a second prod- 11 uct outlet conduit connected to said second product collector and extending from said second chamber; a ninth valve in said second product conduit; a second fuel conduit connected to the lower portion of said second chamber; a tenth valve in said second fuel conduit; a second steam conduit connected to the lower portion of said second chamber; an eleventh valve in said second steam conduit; a second air inlet conduit connected to the lower portion of said second chamber; a twelfth valve in said second air inlet conduit; a second igniter in the lower portion of said second chamber; a pebble outlet conduit in the lower end of said second chamber; an elevator connectingr said pebble outlet conduit from said second chamber and said pebble inlet conduit in said first chamber; an impulse-sequence cycle controller having a plurality of controls therein, a rst control thereof operatively connected to said eighth and ninth valves, a second control 20 12 thereof operatively connected to said fourth and sixth valves and said rst igniter, a seventh control thereof operatively connected to said fth valve, an eighth control operatively connected to said second and third valves; a first differential pressure controller operatively connected to said rst reactant material inlet conduit, said rst product outlet conduit, and said impulse-sequence cycle controller; and a second differential pressure controller operatively connected to said second reactant material inlet conduit, said second product outlet conduit, and said impulse-sequence cycle controller.

ROBERT A. FINDLAY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,310,244 Lassiat Feb. 9, 1943 2,438,261 Utterback Mar. 23, 1948 2,439,730 Happel Apr. 13, 1948 2,470,578 Royster May 17, 1949 2,546,625 Bergstrom Mar. 27, 1951 

1. A SEMI-CONTINUOUS PROCESS FOR CONVERTING HYDROCARBONS TO LOWER BOILING PRODUCTS WHICH COMPRISES HEATING PEBBLES TO A TEMPERATURE OF AT LEAST 1200* F. IN A FIRST CHAMBER OF A PEBBLE HEATER SYSTEM BY DIRECT HEAT EXCHANGE WITH A HOT HEATING GAS; PASSING SAID HOT PEBBLES THROUGH; A SECOND CHAMBER OF SAID PEBBLE HEATER SYSTEM; HEATING HYDROCARBONS TO REACTION TEMPERATURE BY DIRECT CONTACT WITH SAID HOT PEBBLES IN SAID SECOND CHAMBER; REMOVING REACTION PRODUCTS FROM SAID SECOND CHAMBER; RETURNING PEBBLES FROM SAID SECOND TO SAID FIRST CHAMBER; PURGING SAID FIRST AND SECOND CHAMBERS OF HOT HEATING GAS, HYDROCARBONS AND REACTION PRODUCTS UPON EXCESSIVE INCREASE OF PRESSURE DROP THROUGH SAID SECOND CHAMBER; REVERSING OPERATION OF SAID PEBBLE HEATER SYSTEM BY HEATING SAID PEBBLES TO A TEMPERATURE OF AT LEAST 1200* F. BY DIRECT HEAT EXCHANGE WITH A HOT HEATING GAS IN SAID SECOND CHAMBER; PASSING SAID HOT PEBBLES THROUGH SAID FIRST CHAMBER; INTRODUCING HYDROCARBONS INTO DIRECT HEAT EXCHANGE WITH SAID HOT PEBBLES IN SAID FIRST CHAMBER; HEATING SAID HYDROCARBONS TO REACTION TEMPERATURE BY SAID DIRECT CONTACT WITH SAID HOT PEBBLES IN SAID FIRST CHAMBER; REMOVING RESULTING REACTION PRODUCTS FROM SAID FIRST CHAMBER; RETURNING PEBBLES FROM SAID FIRST TO SAID SECOND CHAMBER; PURGING SAID SECOND AND FIRST CHAMBERS OF HOT HEATING GAS, HYDROCARBONS AND REACTION PRODUCTS UPON EXCESSIVE INCREASE OF PRESSURE DROP THROUGH SAID FIRST CHAMBER; AND SIMILARLY REVERSING OPERATION OF SAID PEBBLE HEATER SYSTEM AS PRESSURE DROP THROUGH THE CHAMBER CONTAINING THE HYDROCARBON REACTION BECOMES EXCESSIVE. 